The invention relates to bars comprising synthetic anionic surfactant (e.g., directly esterified fatty acid isethionate or DEFI) and a lesser level of fatty acid soap (anionic/soap system). The invention further relates to process for incorporating alpha or beta hydroxy acid salt (e.g., alpha or beta hydroxy acid salt such as, for example (sodium lactate) while greatly enhancing processability relative to other bars in which the art has attempted to incorporate such hydroxy acid salts.
It has been difficult in the past to produce a manufacturable personal washing bar containing alpha or beta hydroxy acid salts (e.g., sodium lactate or potassium glycolate) because of the deleterious interactions between the salt and either soap or anionic surfactant. As a result, formulations containing, for example, alpha hydroxy acids (AHAS) or AHA salts are extremely soft, sticky and work sensitive. In the subject invention, it has been unexpectedly discovered that a far more processable anionic/soap formulation can be made by adjusting the ratio of hydroxy acid salt (which causes the formulation to be soft and sticky) to calcite filler (which causes the formulation to be hard and crumbly.)
Bars containing anionic surfactant, soap and hydroxy acid salts (e.g., AHA salts) are broadly known. U.S. Pat. No. 4,046,717 to Johnston et al, for example, discloses moisturizing detergent bar (including soap) containing lactate or mixtures of lactate and glutamate. In contrast to subject invention, there is no mention of filler (e.g., calcite filler) or of interaction between filler and alpha hydroxy acid (AHA) salt to improve processability.
Similarly, U.S. Pat. No. 4,268,424 to Hall discloses bar containing surfactant, soap and various moisturizers, but there is no mention of filler, in particular fillers such as calcite or of their interaction with hydroxy acid salts.
U.S. Pat. No. 5,981,451 to Farrell et al. describes a dry mix process (the present invention is generally practiced as melt process) for combining anionic (e.g., DEFI)/soap noodles) with soap and filler. Hydroxy acid salts are not mentioned anywhere.
Applicants have also filed several applications relating to modifying the material properties of formulations containing hydroxy acids or salts. In a co-pending application to Fair et al., filed same date as the subject application, applicants disclose incorporation of relatively high levels of hydroxy acids and/or salts into synthetic surfactant compositions. The compositions generally have pH of about 4-5, preferably close to 4 and, in contrast to compositions of the subject invention, cannot contain soap because of the acidic pH. Further, because of lower pH, these compositions would not tolerate calcite. Fair discloses that hydroxy acids or salts can be made more suitable for extrusion (e.g., less sticky) in formulations containing anionic and hydroxy acids or salts by adding polyol ester (e.g., glycerol monolaurate).
In a separate application, also filed on the same date as the subject application, applicants disclose use of monoglyceride (glycerol monolaurate) to help incorporate hydroxy acid into a soap bar. The application does not, however, disclose use of calcite fillers to enhance processing. Also, it is a soap bar.
In none of the art of which applicants are aware has anyone disclosed that processing can, in formulations comprising anionictsoapihydroxy acid salt (e.g., sodium lactate), be significantly improved by balancing ratio of calcite filler to alkali metal hydroxy acid salt (alpha or beta).